is not so easy for a lot of people. in fact, back at city college when we used to hire teachers, we would have students come in and so let the teachers perform and do a 10-minute gig on the blackboard. and we'd always have a student ask the following question 'cause we wanted to ask a question, which sounded very easy but wasn't. like if you ask the teacher like, "what's the wavelength of the--line with a hydrogen transition?" he could say, "oh, i see, it's a trick." and he say, "oh, i don't know the answer to that, but i'll look it up and i'll tell you next time," 'cause that's a kind of question you know-- we're not supposed to know the answer to, right? but we wanted to ask the prospective instructors a question for which they thought they ought to know the answer, like an easy question. and we found a very, very easy question that not many people could answer. and the reason they couldn't answer is 'cause they didn't have the framework that you guys have right now. and it's this: first of all, we didn't word the question very nicely. we'd have the students say, "hey, when i take an ob
